The present invention relates to a double-acting hydraulic press. It relates to a newly developed double-acting hydraulic press in which the distribution of the output of both the inner press ram and the outer press ram to the total output as a hydraulic press can freely be changed within the range of a fixed total output.
Needless to say, neither in conventional double-acting machine presses, nor in conventional double-acting hydraulic presses, are the output of the inner press ram and the output of the outer press ram independent of each other, nor can the maximum output be separately set for each of them, so it is impossible to use the output of one of them for the other.
By way of illustration, with a double-acting press in which the output of the inner press ram (hereinafter referred to as `inner output`) is 500 tons, and the output of the outer press ram (hereinafter referred to as `outer output`) is 1,100 tons, totalling 1,600 tons, a product which requires a punch resistance of 500 tons and mold compression power of 1,100 tons, by using the above press, can be made to resist against the punch resistance of the inner press ram and against the mold compression power of the outer press ram, thus naturally making possible press processing.
However, in case of a product which is provided with a punch resistance of 850 tons and a mold compressor power of 750 tons, press processing is impossible due to insufficient inner output, even though the total output required of the said press is the same. Further, to making processing possible, even by producing a double-acting press with a performance of 850 tons inner output and 750 tons outer output, in this instance processing becomes impossible due to insufficient mold compression power against a product with a punch resistance of 500 tons and a mold compression power of 1,100 tons.
In order to make processing of the above two products possible, a double-acting press provided with an inner output of 900 tons and an outer output of 1,100 tons, totalling 2,000 tons must be provided, which is both extremely unreasonable as well as uneconomical.